Evaluation of the heart rate response to the Valsalva maneuver

A study has been made of the heart rate (HR) response to the Valsalva maneuver in five different groups of normal white males and two groups of male coronary heart disease (CHD) patients using non-invasive methods. By means of the analysis of variance the effects of age, posture, Valsalva phase and CHD on the HR response were assessed. Both age and CHD were factors that reduce the HR response. Further analysis indicated that the HR change from Phase 3 to Phase 4 in the Valsalva was the preferred discriminator between normals and cardiac patients. We have derived a “Valsalva score” that can be used to identify HR changes that deviate from the expected average normal response for a given age, control HR and Phase 3 HR. HR assessment of the Valsalva maneuver is a simple safe non-invasive test. An abnormal response suggests altered functioning of hemodynamic or autonomic cardiovascular mechanisms governing HR control.     

Improved mitochondrial bioenergetics by anesthetic preconditioning during and after 2 hours of 27 degrees C ischemia in isolated hearts

We examined if sevoflurane given before cold ischemia of intact hearts (anesthetic preconditioning, APC) affords additional protection by further improving mitochondrial energy balance and if this is abolished by a mitochondrial KATP blocker. NADH and FAD fluorescence was measured within the left ventricular wall of 5 groups of isolated guinea pig hearts: (1) hypothermia alone; (2) hypothermia+ischemia; (3) APC (4.1% sevoflurane)+cold ischemia; (4) 5-HD+cold ischemia, and (5) APC+5-HD+cold ischemia. Hearts were exposed to sevoflurane for 15 minutes followed by 15 minutes of washout at 37 degrees C before cooling, 2 hours of 27 degrees C ischemia, and 2 hours of 37 degrees C reperfusion. The KATP channel inhibitor 5-HD was perfused before and after sevoflurane. Ischemia caused a rapid increase in NADH and a decrease in FAD that waned over 2 hours. Warm reperfusion led to a decrease in NADH and an increase in FAD. APC attenuated the changes in NADH and FAD and further improved postischemic function and reduced infarct size. 5-HD blocked the cardioprotective effects of APC but not APC-induced alterations of NADH and FAD. Thus, APC improves redox balance and has additive cardioprotective effects with mild hypothermic ischemia. 5-HD blocks APC-induced cardioprotective effects but not improvements in mitochondrial bioenergetics. This suggests that mediation of protection by KATP channel opening during cold ischemia and reperfusion is downstream from the APC-induced improvement in redox state or that these changes in redox state are not attenuated by KATP channel antagonism.     

The effect of two different renal preservation methods on canine renal allograft survival

Summary Preservation of human cadaver kidneys for transplantation has been achieved primarily by two methods, hypothermic pulsatile perfusion with cryoprecipitated plasma and cold storage with an electrolyte solution. It has been suggested that pulsatile perfusion results in an increased antigenicity of the transplanted kidney. To investigate the possibility that pulsatile perfusion causes changes which may accelerate allograft rejection, machine preservation was compared with simple cold storage. The kidneys were preserved by either one of the two methods for 6 or 24 hours followed by allotransplantation in nephrectomised dogs. No immunosuppressive drugs were given.Kidneys which were allografted without undergoing any preservation (0 hrs) had a mean survival time of 10.4±1.7 days (n=5). Kidneys preserved by machine perfusion for 6 and 24 hours survived for 9.6±1.4 (n=5) and 10.9±1.3 (n=9) days respectively. The mean suryival time for simple cold storage for 6 and 24 hours was 9.3±1.3 (n=7) and 12.0±1.9 (n=6) days. Our findings suggest that in kidneys exposed to minimal warm ischaemia there is no significant difference between the two methods of preservation on renal allograft survival for the time intervals tested.     

A scanning electron microscope study of plaque accumulation on silk and PVDF suture materials in oral mucosa

AIM: To examine plaque accumulation on silk and polyvinylidene fluoride (PVDF) sutures at different time intervals. METHODOLOGY: Twenty-one male albino rabbits received sutures under general and local anaesthesia. After 3, 5 and 7 days sutures were removed and processed for scanning electron microscope (SEM) observation. The Friedman and the Wilcoxon tests were used to compare contamination on PVDF and silk suture materials at different time intervals. RESULTS: At all time intervals, the whole surface of silk sutures was covered with a thick layer of bacterial plaque and debris. Microorganisms and blood cells on the surface and between the filaments of the silk suture material were observed. Light debris appeared around the knot area of PVDF sutures after 3 days. At 5 and 7 days, contamination could be seen in scattered areas along the suture material. The average contaminated area was smaller on PVDF suture materials, which were removed at 5 than at 7 days after insertion. At 3 days, PVDF sutures showed significantly less contamination than at 5 and 7 days (P = 0.002). There were statistically significant differences between silk and PVDF sutures at 3, 5 and 7 days. CONCLUSION: SEM observation showed that PVDF sutures were contaminated less than silk sutures at 3, 5 and 7 days.     

Urinary hexane diamine to assess respiratory exposure to hexamethylene diisocyanate aerosol: a human inhalation study

The use of urinary hexane diamine (HDA) as a biomarker to assess human respiratory exposure to hexamethylene diisocyanate (HDI) aerosol was evaluated. Twenty-three auto body shop workers were exposed to HDI biuret aerosol for two hours using a closed exposure apparatus. HDI exposures were quantified using both a direct-reading instrument and a treated-filter method. Urine samples collected at baseline, immediately post exposure, and every four to five hours for up to 20 hours were analyzed for HDA using gas chromatography and mass spectrometry. Mean urinary HDA (microg/g creatinine) sharply increased from the baseline value of 0.7 to 18.1 immediately post exposure and decreased rapidly to 4.7, 1.9 and 1.1, respectively, at 4, 9, and 18 hours post exposure. Considerable individual variability was found. Urinary HDA can assess acute respiratory exposure to HDI aerosol, but may have limited use as a biomarker of exposure in the workplace.     

Shopping for a transplant: when noncompliant patients seek wait listing at multiple hospitals

United Network for Organ Sharing policy allows patients to be listed for a transplant at multiple hospitals. This strategy can sometimes lessen the transplant waiting time for patients because waiting times vary geographically. We explore the ethical dilemma of "shopping for a transplant" by presenting the case of a patient with an addictive disorder who was listed for liver transplantation at one hospital on the east coast of the United States and was seeking listing at 2 additional hospitals in midwestern United States, when marijuana use was suspected by 1 of the latter 2 facilities. Although the transplant team at this facility deferred listing the patient, the team's bioethicist posed the concept of a duty to notify the facility where the patient was already listed for transplantation about any confirmed substance abuse, in an effort to prevent a scarce resource from being allocated to an individual who is noncompliant.